def transform_raise_stmt(builder: IRBuilder, s: RaiseStmt) -> None:
if s.expr is None:
builder.primitive_op(reraise_exception_op, [], NO_TRACEBACK_LINE_NO)
builder.add(Unreachable())
return
exc = builder.accept(s.expr)
builder.primitive_op(raise_exception_op, [exc], s.line)
builder.add(Unreachable())
def transform_block(builder: IRBuilder, block: Block) -> None:
if not block.is_unreachable:
for stmt in block.body:
builder.accept(stmt)
# Raise a RuntimeError if we hit a non-empty unreachable block.
# Don't complain about empty unreachable blocks, since mypy inserts
# those after `if MYPY`.
elif block.body:
builder.add(RaiseStandardError(RaiseStandardError.RUNTIME_ERROR,
'Reached allegedly unreachable code!',
block.line))
builder.add(Unreachable())
def try_finally_resolve_control(builder: IRBuilder,
cleanup_block: BasicBlock,
finally_control: FinallyNonlocalControl,
old_exc: Value,
ret_reg: Optional[Value]) -> BasicBlock:
"""Resolve the control flow out of a finally block.
This means returning if there was a return, propagating
exceptions, break/continue (soon), or just continuing on.
"""
reraise, rest = BasicBlock(), BasicBlock()
builder.add(Branch(old_exc, rest, reraise, Branch.IS_ERROR))
# Reraise the exception if there was one
builder.activate_block(reraise)
builder.primitive_op(reraise_exception_op, [], NO_TRACEBACK_LINE_NO)
builder.add(Unreachable())
builder.builder.pop_error_handler()
# If there was a return, keep returning
if ret_reg:
builder.activate_block(rest)
return_block, rest = BasicBlock(), BasicBlock()
builder.add(Branch(ret_reg, rest, return_block, Branch.IS_ERROR))
builder.activate_block(return_block)
builder.nonlocal_control[-1].gen_return(builder, ret_reg, -1)
# TODO: handle break/continue
builder.activate_block(rest)
out_block = BasicBlock()
builder.goto(out_block)
# If there was an exception, restore again
builder.activate_block(cleanup_block)
finally_control.gen_cleanup(builder, -1)
builder.primitive_op(keep_propagating_op, [], NO_TRACEBACK_LINE_NO)
builder.add(Unreachable())
return out_block
def except_body() -> None:
builder.assign(exc, builder.primitive_op(false_op, [], -1), line)
out_block, reraise_block = BasicBlock(), BasicBlock()
builder.add_bool_branch(
builder.py_call(builder.read(exit_),
[builder.read(mgr)] + get_sys_exc_info(builder), line),
out_block,
reraise_block
)
builder.activate_block(reraise_block)
builder.primitive_op(reraise_exception_op, [], NO_TRACEBACK_LINE_NO)
builder.add(Unreachable())
builder.activate_block(out_block)
def translate_next_call(builder: IRBuilder, expr: CallExpr,
callee: RefExpr) -> Optional[Value]:
# Special case for calling next() on a generator expression, an
# idiom that shows up some in mypy.
#
# For example, next(x for x in l if x.id == 12, None) will
# generate code that searches l for an element where x.id == 12
# and produce the first such object, or None if no such element
# exists.
if not (expr.arg_kinds in ([ARG_POS], [ARG_POS, ARG_POS])
and isinstance(expr.args[0], GeneratorExpr)):
return None
gen = expr.args[0]
retval = builder.alloc_temp(builder.node_type(expr))
default_val = None
if len(expr.args) > 1:
default_val = builder.accept(expr.args[1])
exit_block = BasicBlock()
def gen_inner_stmts() -> None:
# next takes the first element of the generator, so if
# something gets produced, we are done.
builder.assign(retval, builder.accept(gen.left_expr),
gen.left_expr.line)
builder.goto(exit_block)
loop_params = list(zip(gen.indices, gen.sequences, gen.condlists))
builder.comprehension_helper(loop_params, gen_inner_stmts, gen.line)
# Now we need the case for when nothing got hit. If there was
# a default value, we produce it, and otherwise we raise
# StopIteration.
if default_val:
builder.assign(retval, default_val, gen.left_expr.line)
builder.goto(exit_block)
else:
builder.add(
RaiseStandardError(RaiseStandardError.STOP_ITERATION, None,
expr.line))
builder.add(Unreachable())
builder.activate_block(exit_block)
return retval
def split_blocks_at_uninits(
env: Environment, blocks: List[BasicBlock],
pre_must_defined: 'AnalysisDict[Value]') -> List[BasicBlock]:
new_blocks = [] # type: List[BasicBlock]
# First split blocks on ops that may raise.
for block in blocks:
ops = block.ops
block.ops = []
cur_block = block
new_blocks.append(cur_block)
for i, op in enumerate(ops):
defined = pre_must_defined[block, i]
for src in op.unique_sources():
# If a register operand is not guarenteed to be
# initialized is an operand to something other than a
# check that it is defined, insert a check.
if (isinstance(src, Register) and src not in defined
and not (isinstance(op, Branch)
and op.op == Branch.IS_ERROR)):
new_block, error_block = BasicBlock(), BasicBlock()
new_block.error_handler = error_block.error_handler = cur_block.error_handler
new_blocks += [error_block, new_block]
env.vars_needing_init.add(src)
cur_block.ops.append(
Branch(src,
true_label=error_block,
false_label=new_block,
op=Branch.IS_ERROR,
line=op.line))
raise_std = RaiseStandardError(
RaiseStandardError.UNBOUND_LOCAL_ERROR,
"local variable '{}' referenced before assignment".
format(src.name), op.line)
env.add_op(raise_std)
error_block.ops.append(raise_std)
error_block.ops.append(Unreachable())
cur_block = new_block
cur_block.ops.append(op)
return new_blocks
def gen_return(self, builder: 'IRBuilder', value: Value,
line: int) -> None:
# Assign an invalid next label number so that the next time __next__ is called, we jump to
# the case in which StopIteration is raised.
builder.assign(builder.fn_info.generator_class.next_label_target,
builder.add(LoadInt(-1)), line)
# Raise a StopIteration containing a field for the value that should be returned. Before
# doing so, create a new block without an error handler set so that the implicitly thrown
# StopIteration isn't caught by except blocks inside of the generator function.
builder.error_handlers.append(None)
builder.goto_new_block()
# Skip creating a traceback frame when we raise here, because
# we don't care about the traceback frame and it is kind of
# expensive since raising StopIteration is an extremely common case.
# Also we call a special internal function to set StopIteration instead of
# using RaiseStandardError because the obvious thing doesn't work if the
# value is a tuple (???).
builder.primitive_op(set_stop_iteration_value, [value],
NO_TRACEBACK_LINE_NO)
builder.add(Unreachable())
builder.error_handlers.pop()
def transform_assert_stmt(builder: IRBuilder, a: AssertStmt) -> None:
if builder.options.strip_asserts:
return
cond = builder.accept(a.expr)
ok_block, error_block = BasicBlock(), BasicBlock()
builder.add_bool_branch(cond, ok_block, error_block)
builder.activate_block(error_block)
if a.msg is None:
# Special case (for simpler generated code)
builder.add(RaiseStandardError(RaiseStandardError.ASSERTION_ERROR, None, a.line))
elif isinstance(a.msg, StrExpr):
# Another special case
builder.add(RaiseStandardError(RaiseStandardError.ASSERTION_ERROR, a.msg.value,
a.line))
else:
# The general case -- explicitly construct an exception instance
message = builder.accept(a.msg)
exc_type = builder.load_module_attr_by_fullname('builtins.AssertionError', a.line)
exc = builder.py_call(exc_type, [message], a.line)
builder.primitive_op(raise_exception_op, [exc], a.line)
builder.add(Unreachable())
builder.activate_block(ok_block)
def transform_try_except(builder: IRBuilder,
body: GenFunc,
handlers: Sequence[
Tuple[Optional[Expression], Optional[Expression], GenFunc]],
else_body: Optional[GenFunc],
line: int) -> None:
"""Generalized try/except/else handling that takes functions to gen the bodies.
The point of this is to also be able to support with."""
assert handlers, "try needs except"
except_entry, exit_block, cleanup_block = BasicBlock(), BasicBlock(), BasicBlock()
double_except_block = BasicBlock()
# If there is an else block, jump there after the try, otherwise just leave
else_block = BasicBlock() if else_body else exit_block
# Compile the try block with an error handler
builder.builder.push_error_handler(except_entry)
builder.goto_and_activate(BasicBlock())
body()
builder.goto(else_block)
builder.builder.pop_error_handler()
# The error handler catches the error and then checks it
# against the except clauses. We compile the error handler
# itself with an error handler so that it can properly restore
# the *old* exc_info if an exception occurs.
# The exception chaining will be done automatically when the
# exception is raised, based on the exception in exc_info.
builder.builder.push_error_handler(double_except_block)
builder.activate_block(except_entry)
old_exc = builder.maybe_spill(builder.primitive_op(error_catch_op, [], line))
# Compile the except blocks with the nonlocal control flow overridden to clear exc_info
builder.nonlocal_control.append(
ExceptNonlocalControl(builder.nonlocal_control[-1], old_exc))
# Process the bodies
for type, var, handler_body in handlers:
next_block = None
if type:
next_block, body_block = BasicBlock(), BasicBlock()
matches = builder.primitive_op(
exc_matches_op, [builder.accept(type)], type.line
)
builder.add(Branch(matches, body_block, next_block, Branch.BOOL_EXPR))
builder.activate_block(body_block)
if var:
target = builder.get_assignment_target(var)
builder.assign(
target,
builder.primitive_op(get_exc_value_op, [], var.line),
var.line
)
handler_body()
builder.goto(cleanup_block)
if next_block:
builder.activate_block(next_block)
# Reraise the exception if needed
if next_block:
builder.primitive_op(reraise_exception_op, [], NO_TRACEBACK_LINE_NO)
builder.add(Unreachable())
builder.nonlocal_control.pop()
builder.builder.pop_error_handler()
# Cleanup for if we leave except through normal control flow:
# restore the saved exc_info information and continue propagating
# the exception if it exists.
builder.activate_block(cleanup_block)
builder.primitive_op(restore_exc_info_op, [builder.read(old_exc)], line)
builder.goto(exit_block)
# Cleanup for if we leave except through a raised exception:
# restore the saved exc_info information and continue propagating
# the exception.
builder.activate_block(double_except_block)
builder.primitive_op(restore_exc_info_op, [builder.read(old_exc)], line)
builder.primitive_op(keep_propagating_op, [], NO_TRACEBACK_LINE_NO)
builder.add(Unreachable())
# If present, compile the else body in the obvious way
if else_body:
builder.activate_block(else_block)
else_body()
builder.goto(exit_block)
builder.activate_block(exit_block)
def add_implicit_unreachable(self) -> None:
block = self.blocks[-1][-1]
if not block.ops or not isinstance(block.ops[-1], Return):
self.add(Unreachable())